Methods and apparatus for detecting a signal degradation using the pre-forward error correction bit error rate at an optical transponder

ABSTRACT

In some embodiments, an apparatus comprises an optical transponder which includes a processor, an electrical interface and an optical interface. The processor is operatively coupled to the electrical interface and the optical interface. The optical interface is configured to be operatively coupled to a plurality of optical links and the electrical interface is configured to be operatively coupled to a router such that the optical transponder is configured to be operatively coupled between the plurality of optical links and the router. The processor is configured to perform pre-forward error correction (FEC) bit error rate (BER) detection to identify a degradation of an optical link from the plurality of optical links. The processor is configured to make modifications to packets designated to be transmitted via the optical link in response to the degradation being identified such that the router is notified of the degradation of the optical link.

BACKGROUND

Some embodiments described herein relate generally to methods andapparatus for detecting signal degradation in an optical network. Inparticular, but not by way of limitation, some embodiments describedherein relate to methods and apparatus for detecting a signaldegradation using the pre-forward error correction bit error rate at anoptical transponder.

With a growing demand of optical communication systems with high datarates capability, it is important to promptly detect and notify signaldegradation and failures to satisfy the latency, reliability, andavailability requirements of these optical communication systems, whichinclude optical transponders and routers. When an optical transponderfails, known solutions, however, do not allow a router to be promptlynotified by the optical transponder with which the router interfaces. Asa result, the router is unable to initiate failover procedures promptlyin the event of the failure of the optical transponder, which leads toloss of data traffic. Moreover, known solutions may include respondingto failures (e.g., reroute data traffic) with a latency after failuresoccur. These known solutions, however, are typically unable to detectprognostic indicators of a failure, and thus, unable to implementfailover procedures before the failure actually occurs.

Accordingly, a need exists for a fast method and apparatus topreventively detect a signal degradation in an optical communicationsystem before a failure occurs, and promptly notify a router of theoptical communication system of the failure such that the routerinitiates failover procedures to avoid or minimize traffic loss.

SUMMARY

In some embodiments, an apparatus comprises an optical transponder thatincludes a processor, an electrical interface and an optical interface.The processor is operatively coupled to the electrical interface and theoptical interface. The optical interface is configured to be operativelycoupled to multiple optical links and the electrical interface isconfigured to be operatively coupled to a router such that the opticaltransponder is configured to be operatively coupled between the multipleoptical links and the router. The processor is configured to performpre-forward error correction (FEC) bit error rate (BER) detection toidentify a degradation of an optical link from the multiple opticallinks. The processor is configured to make modifications to packetsdesignated to be transmitted via the optical link in response to thedegradation being identified such that the router is notified of thedegradation of the optical link.

In some embodiments, an apparatus comprises a memory and a processoroperatively coupled to the memory. The processor is configured to beoperatively coupled to a first optical transponder, which is configuredto be operatively coupled to a second optical transponder via multipleoptical links. The second optical transponder is configured to beoperatively coupled to a remote router. The processor is configured tosend first data packets and diagnosis packets to the first opticaltransponder such that the first optical transponder transmits the datapackets to the remote router via the multiple optical links and thesecond optical transponder. The processor is further configured toreceive a signal from the remote router in response to the secondoptical transponder (1) identifying, via pre-forward error correction(FEC) bit error rate detection, a degradation of a first optical linkfrom the multiple optical links, and (2) dropping a subset of thediagnosis packets. The processor is configured to reroute second datapackets in response to the signal such that the remote router receivesthe second data packets via a second optical link from the multipleoptical links.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an optical communication system,according to an embodiment.

FIG. 2 is a block diagram illustrating an optical communication system,according to an embodiment.

FIG. 3 is a graph illustrating a pre-forward error correction (FEC) biterror rate (BER) value of an optical transponder as a function of time,according to an embodiment.

FIG. 4 is a flow chart illustrating a method to detect a degradation byan optical transponder in an optical communication system and notify arouter of the degradation, according to an embodiment.

FIG. 5 is a flow chart illustrating a method to perform a routerswitchover process in response to a notification of a degradation,according to an embodiment.

DETAILED DESCRIPTION

An optical communication system often includes local routerscommunicating with remote routers via an optical network having opticaltransponders and a set of optical links. When the optical transpondersare not co-located with the routers, known solutions typically do notenable the optical transponders to notify the routers of the conditionof the optical links or the optical transponders. As a result, there isoften a time delay for the routers to respond to a signal degradation ora failure associated with the optical links or the optical transponders,which leads to loss of data traffic. Some embodiments described hereinallow an optical transponder to monitor the condition of an optical linkusing pre-forward error correction (FEC) bit error rate (BER) value. Inresponse to the detection of a degradation or a failure of the opticallink, the optical transponder can notify the local routers and/or theremote routers of the degradation or the failure by making modificationsto diagnosis packets, which are communicated between the local routersand the remote routers. Thus, the local routers and the remote routerscan initiate failover procedures (e.g., fast reroute (FRR)) to avoid orminimize traffic loss and achieve a high availability of the opticalcommunication system. In some instances, some embodiments describedherein allow an availability of 99.9999% of the optical communicationsystem. Moreover, some embodiments described herein allow the opticaltransponders to detect the degradation of the optical links andtherefore notify the routers before the optical links fail. Thus, therouters can respond to the degradation preventively before the opticallinks fail, and the data traffic can be transmitted in the opticalcommunication system without interruption.

In some embodiments, an apparatus comprises an optical transponder thatincludes a processor, an electrical interface and an optical interface.The processor is operatively coupled to the electrical interface and theoptical interface. The optical interface is configured to be operativelycoupled to multiple optical links and the electrical interface isconfigured to be operatively coupled to a router such that the opticaltransponder is configured to be operatively coupled between the multipleoptical links and the router. The processor is configured to performpre-forward error correction (FEC) bit error rate (BER) detection toidentify a degradation of an optical link from the multiple opticallinks. The processor is configured to make modifications to packetsdesignated to be transmitted via the optical link in response to thedegradation being identified such that the router is notified of thedegradation of the optical link.

In some embodiments, an apparatus comprises a memory and a processoroperatively coupled to the memory. The processor is configured to beoperatively coupled to a first optical transponder, which is configuredto be operatively coupled to a second optical transponder via multipleoptical links. The second optical transponder is configured to beoperatively coupled to a remote router. The processor is configured tosend first data packets and diagnosis packets to the first opticaltransponder such that the first optical transponder transmits the datapackets to the remote router via the multiple optical links and thesecond optical transponder. The processor is further configured toreceive a signal from the remote router in response to the secondoptical transponder (1) identifying, via pre-forward error correction(FEC) bit error rate detection, a degradation of a first optical linkfrom the multiple optical links, and (2) dropping a subset of thediagnosis packets. The processor is configured to reroute second datapackets in response to the signal such that the remote router receivesthe second data packets via a second optical link from the multipleoptical links.

As used in this specification, the singular forms “a,” “an” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, the term “an optical link” is intended to mean asingle optical link or multiple optical links. For another example, theterm “a bidirectional forwarding detection (BFD) packet” is intended tomean a single BFD packet or multiple BFD packets.

FIG. 1 is a block diagram illustrating an optical communication system,according to an embodiment. The optical communication system 100 can beconfigured to produce, transmit, and/or receive electrical and opticalsignals. For example, the optical communication system 100 can be awavelength division multiplexing (WDM) system, including a densewavelength division multiplexing (DWDM) system. The opticalcommunication system 100 can include routers 101 and 111, opticaltransponders 102 and 112, a network 190, and a set of optical links131-133.

The router 101 can be operatively coupled to the optical transponder102. The router 111 can be operatively coupled to the opticaltransponder 112. The router 101 and the router 111 can be structurallyand/or functionally similar. The router 101 (and the router 111) caninclude general-purpose computational engines that can include, forexample, processors, memory, and/or one or more network interfacedevices (e.g., a network interface card (NIC)). The router 101 (and therouter 111) can also include a field-programmable gate array (FPGA), anapplication specific integrated circuit (ASIC), a combination thereof,or other equivalent integrated or discrete logic circuitry. The router101 (and the router 111) can be networking devices configured to connectat least a portion of a switch fabric system (e.g., a data center orcompute devices within the data center; not shown in the figure) toanother network (e.g., network 190). Examples of the network 190include, but are not limited to, a fiber-optic network (e.g., a localarea network (LAN), metropolitan area network (MAN), wide area network(WAN), or a long-haul network), or a converged optical network havingfunctionalities of both a wireless network and a wired network.

In some embodiments, for example, the router 101 (and the router 111)can enable communication between components (e.g., peripheral processingdevices, portions of the switch fabric; not shown) associated with aswitch fabric system. The communication can be defined based on, forexample, a layer-3 routing protocol. In some embodiments, the router 101(and the router 111) can have one or more network interface devices(e.g., 10 Gb Ethernet devices) through which the router 101 (and therouter 111) can send electrical signals to and/or receive electricalsignals from, for example, a switch fabric and/or other peripheralprocessing devices. The router 101 can also send electrical signals toand/or receive electrical signals from the optical transponder 102; therouter 111 can send electrical signals to and/or receive electricalsignals from the optical transponder 112.

The optical transponder 102 can be operatively coupled to the router101, and operatively coupled to the optical transponder 112 via the setof optical links 131-133. The optical transponder 112 can be operativelycoupled to the router 111. The optical transponder 102 and the opticaltransponder 112 can be structurally and/or functionally similar. Theoptical transponder 102 (and the optical transponder 112) can be anyhigh data rate (e.g., 100 Gbps) optical transceiver such as atransceiver implementing intensity modulation with direct detection,e.g., a coherent optical transceiver, a coherent optical M-aryquadrature amplitude modulation (M-QAM) transceiver, a coherentpolarization-multiplexed (PM) M-QAM transceiver, and/or the like. Theoptical transponder 102 can be configured to receive electrical signalsfrom and/or send electrical signals to the router 101. The opticaltransponder 102 can receive optical signals from and/or send opticalsignals to the optical transponder 112 via one or more optical linksfrom the set of optical links 131-133. Similarly, the opticaltransponder 112 can be configured to receive electrical signals fromand/or send electrical signals to the router 111. The opticaltransponder 112 can receive optical signals from and/or send opticalsignals to the optical transponder 102 via one or more optical linksfrom the set of optical links 131-133. Details of optical transponder102 (or optical transponder 112) are discussed herein with regards toFIG. 2.

In some instances, the optical transponder 102 is disaggregated fromrouter 101, i.e., the optical transponder 102 is located separately fromrouter 101. Similarly stated, the optical transponder 102 and the router101 are not co-located within the same physical device or the equivalentof the same physical device. In some instances, the router 101 cancommunicate with router 111 without the operational knowledge of theoptical transponder 102, the optical transponder 112, and/or the opticallinks 131-133. For example, when the router 101 transmits a data packetand the router 111 is the destination router (or one of the nodes alongthe transmission path), the router 101 has the address (e.g., MediaAccess Control (MAC) address, Internet Protocol (IP) address, and/or thelike) of the router 111. The router 101 does not have the address of theoptical transponder 102, the optical transponder 112, or the set ofoptical links 131-133. Similarly, in some instances, the opticaltransponder 112 is disaggregated from router 111, i.e., the opticaltransponder 112 is located separately from router 111. Similarly stated,the optical transponder 112 and the router 111 are not co-located withinthe same physical device or the equivalent of the same physical device.In some instances, the router 111 can communicate with router 101without the operational knowledge of the optical transponder 112, theoptical transponder 102, and/or the optical links 131-133. For example,when the router 111 transmits a data packet and the router 101 is thedestination router (or one of the nodes along the transmission path),the router 111 has the address (e.g., Media Access Control (MAC)address, Internet Protocol (IP) address, and/or the like) of the router101. The router 111 does not have the address of the optical transponder112, the optical transponder 102, or the set of optical links 131-133.

The set of optical links 131-133 can include a medium capable ofcarrying optical signals. For example, the set of optical links 131-133can include a common optical fiber (or multiple optical fibers) thatinterconnects the optical transponder 102 and the optical transponder112. In some instances, each optical link from the set of optical links131-133 can be included in an individual optical fiber. The opticallinks 131-133 can be included within an optical network that includesother optical links and optical devices (not shown). The number of theoptical links 131-133 shown in the figure is for illustration purposeonly and can include more or less than three optical links.

The number and arrangement of devices shown in FIG. 1 are provided as anexample. In some embodiments, there may be additional devices, fewerdevices, different devices, or differently arranged devices than thoseshown in FIG. 1. For example, the optical communication system 100 caninclude one or more optical devices (not shown in the figure)operatively coupled to the optical transponders 102 and 112. The one ormore optical devices (not shown in the figure) can include one or moreoptical traffic processing and/or optical traffic transfer devices, suchas an optical node, an optical add-drop multiplexer (“OADM”), areconfigurable optical add-drop multiplexer (“ROADM”), an opticalmultiplexer, an optical demultiplexer, an optical transmitter, anoptical receiver, an optical transceiver, a photonic integrated circuit,an integrated optical circuit, a wavelength selective switch, a freespace optics device, a combination of the above, and/or another type ofdevice capable of processing and/or transferring optical traffic. Theone or more optical devices (not shown in the figure) can process anoptical signal and/or transmit an optical signal to another opticaldevice (and/or to optical transponders 102 and 112) via optical links131-133 or a portion of optical links 131-133.

FIG. 2 is a block diagram illustrating an optical communication system,according to an embodiment. The optical communication system 200 can bestructurally and/or functionally similar to the optical communicationsystem 100 in FIG. 1. The optical communication system 200 includesrouters 201 and 252, optical transponders 202 and 251, and a set ofoptical links 231-233. The router 201 can be operatively coupled to theoptical transponder 202. The optical transponder 202 can becommutatively and/or operatively coupled to the optical transponder 251via the set of optical links 231-233. The optical transponder 251 can beoperatively coupled to the router 252. The optical transponder 202 canbe operatively coupled between the set of optical links 231-233 and therouter 201. The optical transponder 251 can be operatively coupledbetween the set of optical links 231-233 and the router 252. The opticaltransponders 202 and 251 can be structurally and/or functionally similarto the optical transponders 102 and 112 in FIG. 1. The routers 201 and252 can be structurally and/or functionally similar to the routers 101and 111 in FIG. 1. The set of optical links 231-233 can be structurallyand/or functionally similar to the set of optical links 131-133 inFIG. 1. The optical transponder 202 can be commutatively coupled, viathe set of optical links 231-233 to a network (not shown in FIG. 2)similar to the network 190 in FIG. 1.

In some instances, the optical transponder 202 is disaggregated fromrouter 201, i.e., the optical transponder 202 is located separately fromrouter 201. Similarly stated, the optical transponder 202 and the router201 are not co-located within the same physical device or the equivalentof the same physical device. In some instances, the router 201 cancommunicate with router 252 without the operational knowledge of theoptical transponder 202, the optical transponder 251, and/or the opticallinks 231-233. For example, when the router 201 transmits a data packetand the router 252 is the destination router (or one of the nodes alongthe transmission path), the router 201 has the address (e.g., MediaAccess Control (MAC) address, Internet Protocol (IP) address, and/or thelike) of the router 252. The router 201 does not have the address of theoptical transponder 202, the optical transponder 251, or the set ofoptical links 231-233. Similarly, in some instances, the opticaltransponder 251 is disaggregated from router 252, i.e., the opticaltransponder 251 is located separately from router 252. Similarly stated,the optical transponder 251 and the router 252 are not co-located withinthe same physical device or the equivalent of the same physical device.In some instances, the router 251 can communicate with router 252without the operational knowledge of the optical transponder 251, theoptical transponder 202, and/or the optical links 231-233. For example,when the router 252 transmits a data packet and the router 251 is thedestination router (or one of the nodes along the transmission path),the router 252 has the address (e.g., Media Access Control (MAC)address, Internet Protocol (IP) address, and/or the like) of the router251. The router 251 does not have the address of the optical transponder251, the optical transponder 202, or the set of optical links 231-233.

The router 201 and the router 252 can be structurally and/orfunctionally similar. The router 201 (and the router 252) can includegeneral-purpose computational engines that can include or be implementedin, for example, processor(s) 248, memory 249, and/or one or morenetwork interface devices (e.g., a network interface card (NIC); notshown in the figure). The router 201 (and the router 252) can alsoinclude a field-programmable gate array (FPGA), an application specificintegrated circuit (ASIC), a combination thereof, or other equivalentintegrated or discrete logic circuitry.

The router 201 can be configured to send diagnosis packets to the router252 to notify the router 252 of a degradation and/or a failure of one ormore components over the transmission path between the router 201 andthe router 252. Similarly, the router 252 can be configured to senddiagnosis packets to the router 201 to detect and/or notify the router201 of a degradation and/or a failure of one or more components over thetransmission path between the router 252 and the router 201. Forexample, the router 201 can detect a degradation and/or a failure at theoptical transponders 202 or 251, the links between the router 201 andthe optical transponder 202, and/or one or more optical links 231-233.

The diagnosis packets can be, for example, bidirectional forwardingdetection (BFD) packets, Ethernet Operations, Administration, andMaintenance (E-OAM) packets (e.g., Ethernet connectivity faultmanagement packets, or link fault management packets), and/or the like.The diagnosis packets can be sent between a local node (e.g., router201) and a remote node (e.g., router 252) at a time interval (e.g.,predetermined time intervals, random time intervals, etc.), by a manualrequest, by an automatic request, and/or in response to meeting acriteria (e.g., the pre-FEC BER value substantially reaching apre-determined threshold). The nodes (i.e., the router 201 and therouter 252) can be configured to support various protocols including,for example, BGP (Border Gateway Protocol), EIGRP (Enhanced InteriorGateway Routing Protocol), IS-IS (Intermediate System-to-IntermediateSystem), OSPF (Open Shortest Path First), or HSRP (Hot Standby RouterProtocol). These protocols detect forwarding path detection failures andallow failure messages to be transmitted.

During an initial BFD session setup, each router defines a BFD controlpacket, which is sent to the neighbor (peer) router to establish a BFDsession. The initial BFD control packet at a first router (e.g., router201) includes a first field identifying itself (e.g., a media accesscontrol (MAC) address of router 201) and a second field identifying asecond router (e.g., a MAC address of router 252). Similarly, theinitial BFD control packet at a second router (e.g., router 252)includes a first field identifying itself (e.g., a MAC address of router252) and a second field identifying a second router (e.g., the MACaddress of router 201). When router 201 and router 252 both have theirown identifiers in each other's BFD control packets, a BFD sessionbetween the router 201 and the router 252 is established.

Once a BFD session is created, the local node (e.g., router 201) and theremote node (e.g., router 252) can operate in an asynchronous mode anduse an Echo function. For example, diagnosis packets (e.g., Echopackets; also referred herein to as BFD packets) can be sent from thelocal (originating) node to the remote node, and the remote node cansend the diagnosis packets back to the local (originating) node. In someinstances, the diagnosis packets that are sent from the remote node backto the local node can be the same diagnosis packets that are sent fromthe local node to the remote node. In other instances, certain fields(e.g., origination address, destination address, etc.) of the diagnosispackets that are sent from the remote node back to the local node arechanged and therefore different from the fields of the diagnosis packetsthat are sent from the local node to the remote node. In some instances,when a node receives a BFD packet within a detect-timer period, the BFDsession remains up and any routing protocol associated with BFDmaintains its adjacencies (i.e., the association between the local nodeand the remote node during the BFD session). If a number of the echoedBFD packets are not received, the BFD session is considered to be downand the local node informs any routing protocols of that BFD sessionabout the failure. The local node reroutes traffic (e.g., initiate aFast Reroute or convergence process) to bypass the failed link, node, orinterface. The local node then sends a failure notification packet tothe remote node to notify the remote node of the failure such that theremote node can initiate rerouting traffic (e.g., fast reroute orconvergence) without waiting on its slower failure detection to identifythe failure.

The router can be configured to include capabilities to executefunctions based on fast reroute protocols, which allow rapid recovery inthe event of a failure of a network link or a network node. In a networkemploying Fast Reroute (“FRR”) (e.g., a network implementingMultiprotocol Label Switching (MPLS) Traffic Engineering), trafficflowing through a failed link or node is rerouted through one or morepreconfigured backup paths. For example, in the event of a degradationor a failure of the optical link 232, the routers 201 and 252 caninitiate Fast Reroute and direct traffic to another optical link (e.g.,optical link 231) or through optical transponders other than opticaltransponders 202 and 251.

The processor 248 can be or include any processing device or componentconfigured to perform the data collecting, processing and transmittingfunctions as described herein. The processor 248 can be configured to,for example, write data into and read data from the memory 249, andexecute the instructions stored within the memory 249. Processor 248 canalso be configured to execute and/or control, for example, theoperations of the memory 249. In some implementations, based on themethods or processes stored within the memory 249, the processor 248 canbe configured to execute a router switchover process, as described inFIG. 5.

The memory 249 can be, for example, a random-access memory (RAM) (e.g.,a dynamic RAM, a static RAM), a flash memory, a removable memory, and/orso forth. In some embodiments, the memory 249 can include, for example,one or more of a database, process, application, virtual machine, and/orsome other software modules (stored and/or executing in hardware) orhardware modules configured to execute a router switchover process. Insuch implementations, instructions of executing the router switchoverprocess and/or the associated methods can be stored within the memory249 and executed at the processor 248.

The optical transponder 202 (or the optical transponder 251) can be anyhigh data rate (e.g., 100 Gbps) optical transceiver such as atransceiver implementing intensity modulation with direct detection,e.g., a coherent optical transceiver, a coherent optical M-aryquadrature amplitude modulation (M-QAM) transceiver, a coherentpolarization-multiplexed (PM) M-QAM transceiver, and/or the like. Theoptical transponder 202 can be configured to receive electrical signalsfrom and/or send electrical signals to the router 201. The opticaltransponder 202 can receive optical signals from and/or send opticalsignals to the optical transponder 251 via one or more optical linksfrom the set of optical links 231-233.

The optical transponder 202 (or the optical transponder 251) can includean electrical interface 203, an optical interface 204, electricalcomponents 205, optical components 206, and a controller 207. Theelectrical components 205 can include a forward error correction (FEC)encoder 212, a forward error correction (FEC) decoder 222, adigital-to-analog converter (DAC) 214, and an analog-to-digitalconverter (ADC) 224. The optical components can include a transmitoptical sub-assembly (TOSA) 216 and a receiver optical sub-assembly(ROSA) 226. The controller 207 can include a processor 241 and a memory242. Each component of the optical transponder 202 can be operativelycoupled to another component of the optical transponder 202.

The number and arrangement of components shown in FIG. 2 are provided asan example. In some embodiments, there may be additional components,fewer components, different components, or differently arrangedcomponents than those shown in FIG. 2. For example, the opticaltransponder 202 can include a digital signal processor (DSP) (not shownin the figure) which can receive the electrical signals from the FECencoder and perform appropriate signal processing such as spectralshaping, equalization for optical and electrical impairments, and othersuch signal processing to ensure that the highest fidelity transmitwaveforms with desired characteristics are transmitted into the opticalcommunication system 200. For another example, each component of theoptical transponder 202 can access a memory component (e.g., memory 242)and share the use of the memory component.

When the optical transponder 202 transmits traffic from west to east,the FEC encoder 212, the DAC 214, and the TOSA 216 together transmittraffic to the optical transponder 251 via the optical links 231-233.When the optical transponder 202 receives traffic from east to west, theROSA 226, the ADC 224, and the FEC decoder 222 receive traffic from theoptical transponder 252 via the optical links 231-233.

The FEC encoder 212 can be or can include a general purpose processor, afield-programmable gate array (FPGA), an application specific integratedcircuit (ASIC), a combination thereof, or other equivalent integrated ordiscrete logic circuitry. The FEC encoder 212 can also include a memory(e.g., a random-access memory (RAM) (e.g., a dynamic RAM, a static RAM),a flash memory, a removable memory, and/or so forth.) Forward ErrorCorrection (FEC) is a technique for transmitting data such thattransmission errors may be minimized. FEC coding redundantly codes eachbit to allow a receiving decoder to detect and correct transmissionerrors. Specifically, for example, the FEC encoder 212 can receive a setof electrical signals (having data signals and/or data packets) from theelectrical interface 203 (or from a network processor located upstream(e.g., router 201)), and encodes the set of electrical signals based ona pre-determined algorithm. The FEC encoder 212 can generate FECoverhead bits and add the FEC overhead bits to a payload of anelectrical signal. The FEC overhead bits are encoded such that theoptical transponder 251 (or the FEC decoder in the optical transponder251) can use the information within the FEC overhead bits to detect andcorrect bit errors in the payload of the electrical signal received bythe optical transponder 251 after converting the related optical signal.Bit errors may be incurred in the transmission path (e.g., the opticalcomponents 206 of the optical transponders 202 or 251, and/or theoptical links 231-233) between the optical transponder 202 and opticaltransponder 251.

The DAC 214 can receive the digital electrical signals from the FECencoder 212 and convert those signals to analog electrical signals. Theanalog electrical signals can then be sent to the optical components206. The DAC 214 can be or can include a general purpose processor, afield-programmable gate array (FPGA), an application specific integratedcircuit (ASIC), a combination thereof, or other equivalent integrated ordiscrete logic circuitry. The DAC 214 can also include a memory (e.g., arandom-access memory (RAM) (e.g., a dynamic RAM, a static RAM), a flashmemory, a removable memory, and/or so forth.)

The transmit optical sub-assembly (TOSA) 216 includes optical componentsthat receive electrical signals from the DAC 214 and convert theseelectrical signals into modulated optical signals. For example, the TOSA216 can modulate an optical source signal with the electrical signals togenerate a set of optical signals carrying the information contained inthe electrical signals. The TOSA 216 can also include optical sources(e.g., a tunable laser), drivers, modulators, splitters, combiners,attenuators, amplifiers, polarization rotators, power meters, and alike.The TOSA 216 transmits the optical signal to the optical interface 204which then transmits the optical signals to the network (not shown inthe figure; similar to the network 190 as in FIG. 1) via a singleoptical fiber (or multiple optical fibers). The single optical fiber (ormultiple optical fibers) can include one or more optical links 231-233.

The FEC decoder 222 can be configured to correct bit errors in datatransmission from the remote router 252 or the optical transponder 251over the transmission path (e.g., the optical components 206 of theoptical transponders 202 or 251, and/or the optical links 231-233) toimprove data reliability. The FEC decoder 222 can be or can include ageneral purpose processor, a field-programmable gate array (FPGA), anapplication specific integrated circuit (ASIC), a combination thereof,or other equivalent integrated or discrete logic circuitry. The FECdecoder 222 can also include a memory (e.g., a random-access memory(RAM) (e.g., a dynamic RAM, a static RAM), a flash memory, a removablememory, and/or so forth.) The FEC decoder 222 can receive a set ofelectrical signals, each having a payload together with FEC overheadbits from the ADC 224, and detect and correct bit errors that haveoccurred over the transmission path, and recover the data informationincluded in the set of electrical signals. In one implementation, theFEC encoder 212 and the FEC decoder 222 can implement quasi-cycliclow-density parity-check (QC-LDPC) codes.

The FEC decoder 222 can be configured to measure the bit error rate(BER), which represents the number of bit errors per unit time. In someinstances, in addition to mearing the bit error rate, the FEC decoder222 can be configured to measure the bit error ratio, which representsthe number of bit errors divided by the total number of transferred bitsduring a time interval. The bit error rate or the bit error ratio canshow a degree of errors that has occurred over the transmission path(e.g., the optical components 206 of the optical transponders 202 or251, and/or the optical links 231-233). The FEC decoder 222 can beconfigured to measure the BER value before or after the FEC decoder 222corrects the bit errors. The BER value measured before the FEC decoder222 corrects the bit errors is referred to as pre-FEC BER value. Thepre-FEC BER value can be used as an indication of signal degradationover the transmission path. The signal degradation can occur at one ormore optical links (e.g., optical link 232) or anywhere over thetransmission path between an optical transmitter or an optical receiver.For example, if data packets are transmitted from the opticaltransponder 202 to the optical transponder 251, the pre-FEC BER valuemeasured by the FEC decoder (not shown in the figure) at the opticaltransponder 251 can be an indicator of signal degradation at one or moreoptical links 231-233 or anywhere between the FEC encoder 212 of theoptical transponder 202 and the FEC decoder (not shown in the figure) ofthe optical transponder 251.

The ADC 224 can receive the analog electrical signals from the opticalcomponents 206 and convert those signals to digital electrical signals.The digital electrical signals can then be sent to the FEC decoder 222.The ADC 224 can be or can include a general purpose processor, afield-programmable gate array (FPGA), an application specific integratedcircuit (ASIC), a combination thereof, or other equivalent integrated ordiscrete logic circuitry. The ADC 224 can also include a memory (e.g., arandom-access memory (RAM) (e.g., a dynamic RAM, a static RAM), a flashmemory, a removable memory, and/or so forth.)

The receiver optical sub-assembly (ROSA) 226 can receive optical signalsfrom the network (not shown in the figure; similar to the network 190 asin FIG. 1) via one or more optical links 231-233 in a single opticalfiber (or multiple optical fibers), and convert the optical signals intoelectrical signals. The ROSA 226 can transmit the electrical signals tothe ADC 224. The ROSA 226 can include optical hybrids, photodetectors,transimpedance amplifiers and attenuators, and alike.

The controller 207 can include components and/or circuitry configured tocontrol properties of an optical signal, an electrical signal, and/orsend control signals to one or more components of optical transponder202. For example, controller 207 can send control signals to and thuscontrol properties of one or more components within the electricalcomponents 205 and/or one or more components within the opticalcomponents 206. In some instances, controller 207 can send controlsignals to the electrical components 205 or the optical components 206such that the electrical components 205 or the optical components 206drop (or remove) a subset of, a predetermined number of, or the entiretyof the diagnosis packets (e.g., BFD packets) that are transmittedbetween the router 201 and the router 252. In some instances, controller207 can send control signals to the electrical components 205 or theoptical components 206 to generate a copy of the diagnosis packets(e.g., BFD packets) and store the copy of the diagnosis packets (e.g.,at the memory 242). In some instances, controller 207 can change thestate (Sta) field in the diagnosis packets to “Down” such that therouters 201 and 252 are notified of the failure.

In some implementations, the controller 207 is a hardware device and/orsoftware (executed on a processor and/or stored in memory) external tothe optical components 206. In other implementations, controller 207 isa hardware device and/or software (executed on a processor and/or storedin memory) implemented within the optical components 206. The controller207 can include a processor 241 and a memory 242 operatively coupled tothe processor 241. The processor 241 can be or include any processingdevice or component configured to perform the data collecting,processing and transmitting functions as described herein. The processor241 can be configured to, for example, write data into and read datafrom the memory 242, and execute the instructions stored within thememory 242. Processor 241 can also be configured to execute and/orcontrol, for example, the operations of the memory 242. In someimplementations, based on the methods or processes stored within thememory 242, the processor 241 can be configured to execute thedegradation detection and notification process, as described in FIG. 4.

The memory 242 can be, for example, a random-access memory (RAM) (e.g.,a dynamic RAM, a static RAM), a flash memory, a removable memory, and/orso forth. In some embodiments, the memory 242 can include, for example,a database, process, application, virtual machine, and/or some othersoftware modules (stored and/or executing in hardware) or hardwaremodules configured to execute a degradation detection and notificationprocess as described further herein. In such implementations,instructions of executing the degradation detection and notificationprocess and/or the associated methods can be stored within the memory242 and executed at the processor 241.

The electrical interface 203 allows the exchange of electrical signalsbetween the router 201 and the optical transponder 202. The electricalinterface 203 can include and/or be configured to manage one or multipleelectrical ports of the optical transponder 202. In some instances, forexample, the electrical interface 203 can include one or more linecards, each of which can include one or more ports (operatively) coupledto devices (e.g., router 201). A port included in the electricalinterface 203 can be any entity that can communicate with a coupleddevice or over a network. In some embodiments, such a port need notnecessarily be a hardware port, but can be a virtual port or a portdefined by software. In some embodiments, the connections between theelectrical interface 203 and the devices in the optical communicationsystem 200 can be implemented via a physical layer using, for example,electrical cables, wireless connections, or other suitable connectionmeans. In some embodiments, the electrical interface 203 can be anEthernet interface.

The optical interface 204 allows the exchange of optical signals betweenthe optical transponder 202 and the network (not shown in the figure;similar to network 190 in FIG. 1) or optical devices in the opticalcommunication system 200. The optical interface 204 can include and/orbe configured to manage one or multiple optical ports of the opticaltransponder 202.

Each optical link from the set of optical links 231-233 can include amedium capable of carrying optical signals. For example, optical link231 can include an optical fiber that interconnects optical transponders202 and 251 via optical ports (not shown) of the optical interface 204and optical ports of the optical interface (now shown) of the opticaltransponder 251. The optical link 231 can be included within an opticalcommunication system 200 that includes other optical links and opticaldevices. The set of optical links 231-233 can carry optical signals withdifferent wavelengths (e.g., colored interface).

In use, the router 201 can send a set of electrical signals (having datapackets and diagnosis packets) to the electrical interface 203 of theoptical transponder 202. The diagnosis packets can be bidirectionalforwarding detection (BFD) packets, Ethernet Operations, Administration,and Maintenance (E-OAM) packets (e.g., Ethernet connectivity faultmanagement packets, or link fault management packets), and/or the like.The diagnosis packets can be sent between the router 201 and the router252 at a time interval. For example, once a diagnosis session (e.g., aBFD session) is created, the router 201 and router 252 can operate in anasynchronous mode and use an Echo function. For example, diagnosispackets (e.g., Echo packets; also referred herein to as BFD packets) canbe sent from the router 201 and the router 252 via the opticaltransponder 202, the optical links 231-233 and the optical transponder251, and the router 252 sends the packets back to the router 201 alsovia the optical transponder 251, the optical links 231-233 and theoptical transponder 202, and the router 202. In some instances, thediagnosis packets that are sent from the router 252 to the router 201can be the same diagnosis packets that are sent from the router 201 tothe router 252. In other instances, certain fields (e.g., originationaddress, destination address, etc.) of the diagnosis packets that aresent from the router 252 back to the router 201 are changed andtherefore different from the fields of the diagnosis packets that aresent from the router 201 to the router 252. In some instances, when therouter 201 or 252 receives a BFD packet within a detect-timer period,the BFD session remains up and any routing protocol associated with BFDmaintains its adjacencies (i.e., the association between the router 201and the router 252 during the BFD session). If a number of the echoedBFD packets are not received, the BFD session is considered to be down(in operation) and the local router (router 201 or 252) informs anynetwork device using routing protocols and for that BFD session aboutthe interruption of the BFD session.

Upon receiving the set of electrical signals from the electricalinterface 203, the FEC encoder 212 can encode the set of electricalsignals with FEC overhead bits and send the combination to the DAC 214to convert to analog electrical signals. TOSA 216 can modulate anoptical source signal with the analog electrical signals received fromDAC 214 and generate a set of optical signals carrying the informationof the data packets and the diagnosis packets. The set of opticalsignals can be sent through the optical interface 204 to the opticaltransponder 251 via the set of optical links 231-233. In some instances,some optical signals from the set of optical signals have differentwavelengths. Each optical signal from the set of optical signals istransmitted via an optical link from the set of optical links 231-233.Each optical link from the set of optical links is uniquely associatedwith a wavelength from the set of wavelengths.

In some instances, for example, when an optical link 232 is notfunctioning normally (e.g., the optical fiber deteriorates), more biterrors may occur when the set of optical signals are transmitted via theoptical link 232. Upon receiving the set of optical signals, the ROSA(not shown in the figure; functionally and structurally similar to theROSA 226) of the optical transponder 251 can convert the set of opticalsignals to a set of electrical signals (including the data packets andthe diagnosis packets) and can send to the ADC (not shown in the figure;functionally and structurally similar to the ADC 224) of the opticaltransponder 251. The ADC of the optical transponder 251 can convert theset of (analog) electrical signals to a set of digital electricalsignals and send to the FEC decoder (not shown in the figure;structurally and functionally similar to the FEC decoder 222) of theoptical transponder 251. Upon receiving the set of digital electricalsignals, the FEC decoder of the optical transponder 251 can measure thepre-FEC BER value of the set of digital electrical signals before theFEC decoder of the optical transponder 251 corrects the bit errors thathave occurred during the transmission of the set of optical signals overthe degrading optical link 232. The pre-FEC BER value can be used as anindication of signal degradation over the transmission path. The signaldegradation can occur at one or more optical links (e.g., optical link232) or anywhere over the transmission path between the opticaltransponder 202 and the optical transponder 251.

When the pre-FEC BER value measured by the FEC decoder of the opticaltransponder 251 reaches or substantially reaches a pre-determinedthreshold (i.e., a first threshold), the FEC decoder of the opticaltransponder 251 can generate a signal indicating that the threshold (orthe first threshold) of a signal degradation of the optical link 232 ismet. In some instances, the signal can include an identifier of theoptical link 232 when the threshold of the signal degradation of theoptical link 232 is met. In some instances, the pre-FEC BER valuesubstantially reaches the pre-determined threshold when the pre-FEC BERvalue is within a certain range of the pre-determined threshold (e.g.,within 5% difference of the pre-determined threshold). In someimplementations, the pre-determined threshold is adjustable (e.g., by anetwork administrator.)

In response to the detection of the signal degradation of the opticallink 232, the optical transponder 251 (e.g., similar to the processor241 of the controller 207) can make modifications to the diagnosispackets. In some implementations, the optical transponder 251 (e.g.,processor 241 of the controller 207) can drop (or remove) a subset of, apredetermined number of, or the entirety of the diagnosis packets. Inother words, the optical transponder 251 can include the set ofelectrical signals having information associated with the data packetsand not having information associated with the diagnosis packets thathave been dropped (or having information associated with only a subsetof the diagnosis packets that have been dropped). The FEC decoder of theoptical transponder 251 can correct the FEC bit errors of the electricalsignals to produce a corrected set of electrical signals and send thecorrected set of electrical signals to the router 252.

Upon receiving, from the optical transponder 251, the set of electricalsignals having information associated with the data packets and nothaving information associated with the diagnosis packets that have beendropped (or having information associated with only a subset of thediagnosis packets that have been dropped), the router 252 can detect themodifications made to the diagnosis packets. In response, the router 252can (1) initiate the failure response mechanisms (e.g., reroute traffic,initiate a Fast Reroute or convergence process), (2) modify a field ofthe diagnosis packets to “Down” indicating that the diagnosis packetshave been modified or dropped and in some instances, send the modifieddiagnosis packets back to the router 201, or (3) a combination of (1)and (2). For example, in the event of a degradation or a failure of theoptical link 232, the router 252 can initiate Fast Reroute and directcurrent and/or future traffic to a different optical link (e.g., opticallink 231) or through optical transponders other than opticaltransponders 202 and 251. In some instances, the router 252 can wait totake actions until the pre-FEC BER value reaches a second threshold (asdiscussed below with regards to FIG. 3) to initiate the failure responsemechanisms.

When the router 252 does not receive the diagnosis packets (or onlyreceives a portion of the diagnosis packets) from the opticaltransponder 251, the router 252, in response, does not send echoeddiagnosis packets back to the router 201. The BFD session between therouter 201 and the router 252 is considered to be down, and the router201 is notified of the signal degradation of the optical link 232 inresponse to not receiving the echoed diagnosis packets from the router252. In response, the router 201 can initiate the failure responsemechanisms (e.g., reroute traffic, initiate a Fast Reroute orconvergence process) to bypass the degrading link 232. In suchinstances, the router 201 can be notified of the degradation of theoptical link 232 sooner than would be the case of solely waiting on itsslower failure detection to identify the failure (e.g., a mechanismsolely performed at and using information at router 201). In suchinstances, the notification time of the router 201 (i.e., the time ittakes to notify router 201 of the signal degradation) is around the BFDmultiplier times the minimum-interval value. The minimum-interval valueis the value of the minimum interval, in microseconds, between thereceived BFD packets less any jitter applied by the transmitting router.When the minimum-interval value is zero, the transmitting system doesnot receive any periodic BFD packets from the remote system. The BFDmultiplier, in some instances, is referred to as the detection timemultiplier. The negotiated transmit interval, multiplied by the BFDmultiplier, provides the detection time for the receiving system in anasynchronous mode.

In some implementations, instead of making modifications to thediagnosis packets at the optical transponder 251 and waiting for router252 to detect the modifications of the diagnosis packets, the opticaltransponder 251 can generate a copy of the diagnosis packets and storethe copy of the diagnosis packets at the memory of the opticaltransponder 251. In response to the detection of the signal degradationof the optical link 232, the optical transponder can change the state(Sta) field in the copy of the diagnosis packets to “Down” and send thecopy of the diagnosis packets to the optical transponder 202 and therouter 252. The optical transponder 202 can transmit the copy of thediagnosis packets to router 201. Based on the “Down” field of the copyof the diagnosis packets, the router 201 can initiate the failureresponse mechanisms to bypass the degrading link. In suchimplementations, the notification time to routers 201 and 252 can benearly instantaneous (i.e., based on transmission and not requiringadditional processing). In such implementations, the BFD session betweenrouters 201 and 252 is not authenticated or with simple authentication.In some instances, the simple authentication can be simple passwordauthentication. In such instances, one or more passwords (withcorresponding key identifiers) are configured in each transmittingsystem and/or each receiving system and one of these passwords oridentifier pairs is carried in each BFD packet. The receiving systemaccepts the packet if the password and the key identifiers match one ofthe passwords or identifier pairs configured in that receiving system.In some implementations, the optical transponder 251 can makemodifications to the diagnosis packets and send to router 252 to notifyrouter 252 of the signal degradation. In the meantime, the opticaltransponder 251 can also generate a copy of the diagnosis packets,change the state (Sta) field to “Down”, and send to router 201 via theoptical transponder 202.

By using the pre-FEC BER value as an indicator of a signal degradationof an optical link, routers 201 and 252 can respond (e.g., initiate FRR)before a failure of the optical link actually occurs. Suchimplementations notify the routers of signal degradation and allowrouters to preventively reroute traffic to bypass a degrading link suchthat traffic loss is avoided or minimized in the event of a failure. Inother words, in these implementations, the data traffic can betransmitted in the optical communication system 200 with zero or minimuminterruption. Moreover, the optical transponder 251 need not (and doesnot) send control signals to the routers 252 or 201 to notify therouters 251 and 201 of the signal degradation. Instead, by modifying thediagnosis packets (e.g., dropping BFD packets) based on the pre-FEC BERvalue, the diagnosis session (e.g., the BFD session) between routers 201and 252 can be considered and communicated as down. In response to notreceiving the diagnosis packets after a time interval, the routers 201and 252 are notified of the signal degradation and can initiate failureresponse mechanisms (e.g., FRR).

FIG. 3 is a graph illustrating an example of a pre-FEC BER value 302 ofan optical transponder as a function of time 301, according to anembodiment. In some implementations, upon receiving a set of opticalsignals via a set of optical links (e.g., the set of optical links231-233 in FIG. 2), an optical transponder (e.g., optical transponder251 in FIG. 2) can convert the set of optical signals to a set ofelectrical signals and measure the pre-FEC BER value 302 of the set ofelectrical signals. The FEC decoder of the optical transponder canmeasure the pre-FEC BER value before the FEC decoder corrects the biterrors that have occurred during the transmission of the set of opticalsignals. The pre-FEC BER value 302 can be used as an indication of asignal degradation over the transmission path. The signal degradationcan occur at one or more optical links (e.g., optical link 232 in FIG.2) or anywhere over the path between an optical transmitter and anoptical receiver.

In some implementations, user-configurable thresholds (e.g., 303, 305,307, 308) can be set to trigger notifications of signal degradationand/or failures. For example, when the pre-FEC BER value issubstantially below a first threshold 303 (i.e., the FEC degradethreshold), it is considered that the transmission path functionsproperly and the optical transponder does not trigger any notificationsof signal degradation and/or failures. The pre-FEC BER valuesubstantially meets a criteria (e.g., below a threshold, exceeds athreshold, or between a first threshold and a second threshold) when thepre-FEC BER value is within a range of the criteria (e.g., 5% of a firstthreshold).

When the pre-FEC BER value substantially exceeds the first threshold 303(e.g., more than 5% of the first threshold), in some implementations,the optical transponder can be set to trigger the notification of signaldegradation. When the optical transponder is set to trigger thenotification of signal degradation, the optical transponder can makemodifications to diagnosis packets (e.g., BFD packets). For example, theoptical transponder can drop (or remove) a subset of, a predeterminednumber of, or the entirety of the diagnosis packets (e.g., BFD packets)that are transmitted between a local router and a remote router (e.g.,routers 201 and 252 in FIG. 2). In response to not receiving thediagnosis packets for a period of time, the local router and the remoterouter can initiate failure response mechanisms (e.g., reroute traffic,initiate a Fast Reroute or convergence process). For another example,the optical transponder can replay the diagnosis packets (e.g., bymaking a copy of the diagnosis packets and storing these copies at theoptical transponder) and change the state (Sta) field in the diagnosispackets to “Down”. The optical transponder can then send the modifieddiagnosis packets to the routers to notify the routers of the signaldegradation. In response, the routers can initiate failure responsemechanisms.

In some implementations, when the pre-FEC BER value substantiallyexceeds the first threshold 303, the optical transponder can postponetriggering the notification of signal degradation for a pre-determinedperiod of time (i.e., the FEC degrade window 304). In some instances,the pre-determined period of time is user-configurable. When thepre-determine period of time 304 ends and the pre-FEC BER value stillexceeds the first threshold 303, the optical transponder can be set totrigger the notification of signal degradation 307. The opticaltransponder can make modifications to diagnosis packets (e.g., BFDpackets), for example, by dropping the diagnosis packets and/orreplaying the diagnosis packets and changing the state filed in thediagnosis packets to “Down”.

In some implementations, when the pre-FEC BER value substantiallyexceeds a second threshold 305 (i.e., the FEC FAIL threshold), theoptical transponder can be set to trigger the notification of signalfailure. In some implementations, the optical transponder can postponetriggering the notification of signal failure for a pre-determinedperiod of time (i.e., the FEC fail window 306). When the pre-determinedperiod of time 306 ends and the pre-FEC BER value still exceeds thesecond threshold 305, the optical transponder can be set to trigger thenotification of signal failure 308.

FIG. 4 is a flow chart illustrating a method 400 to detect a degradationby an optical transponder in an optical communication system and notifya router of the degradation, according to an embodiment. The degradationdetection and notification method 400 can be executed at, for example, aprocessor such as the processor 241 of the controller 207 shown anddescribed with respect to FIG. 2.

At 401, an optical transponder in the optical communication systemreceives data packets and diagnosis packets via an optical link from aset of optical links. The diagnosis packets can be bidirectionalforwarding detection (BFD) packets, Ethernet Operations, Administration,and Maintenance (E-OAM) packets (e.g., Ethernet connectivity faultmanagement packets, or link fault management packets), and/or the like.The diagnosis packets can be sent between a local router and a remoterouter at a time interval. A remote router (e.g., router 201) can send aset of electrical signals (having the data packets and the diagnosispackets) destined for a remote optical transponder (e.g., the opticaltransponder 202 in FIG. 2), which encodes the set of electrical packetswith FEC overhead bits by a FEC encoder to produce a set of encodedelectrical packets and converts the set of encoded electrical packets toa set of optical signals. The set of optical signals are transmitted viaa set of optical links (e.g., the set of optical links 231-233 in FIG.2) to a local optical transponder (e.g., optical transponder 251 in FIG.2).

At 402, the local optical transponder converts the set of opticalsignals to a set of electrical signals and performs pre-forward errorcorrection (FEC) bit error rate (BER) detection to identify adegradation of the transmission path that includes the optical link fromthe set of optical links. A FEC decoder of the local optical transpondercan measure, based on the FEC overhead bits, the pre-FEC BER valuebefore the FEC decoder corrects the bit errors that have occurred duringthe transmission of the set of optical signals over the degradingtransmission path that includes optical link of the set of opticallinks. The pre-FEC BER value can be used as an indication of signaldegradation over the transmission path. The signal degradation can occurat one or more optical links or anywhere over the path between theremote optical transponder and the local optical transponder 251.

When the pre-FEC BER value measured by the FEC decoder of the localoptical transponder reaches or substantially reaches a pre-determinedthreshold (i.e., a first threshold), the FEC decoder can generate asignal indicating that the threshold (or the first threshold) of asignal degradation of the optical link is met. In response to thedetection of the signal degradation of the optical link, the localoptical transponder can make modifications to the diagnosis packets. Forexample, at 403, the local optical transponder can drop a subset of, apredetermined number of, or the entirety of the diagnosis packets inresponse to the identifying of the degradation of the optical link.

At 404, the local optical transponder can correct the FEC bit errors andsend the corrected set of electrical signals (having the data packets)to a local router (e.g., router 252 in FIG. 2) operatively coupled tothe local optical transponder to notify the local router of thedegradation of the optical link in response to the dropping of thesubset of (or a predetermined number of, or the entirety of) thediagnosis packets. In response, the local router can (1) initiate thefailure response mechanisms (e.g., reroute traffic, initiate a FastReroute or convergence process), (2) modify a field of the diagnosispackets to “Down” indicating that the diagnosis packets have beenmodified or dropped and in some instances, send the modified diagnosispackets back to the remote router, or (3) a combination of (1) and (2).For example, in the event of a degradation or a failure of the opticallink, the local router can initiate Fast Reroute and direct currentand/or future traffic to a different optical link or through opticaltransponders other than the local optical transponder and the remoteoptical transponder. In some instances, the local router can wait totake actions until the pre-FEC BER value reaches a second threshold (asdiscussed with regards to FIG. 3) to initiate the failure responsemechanisms.

When the local router does not receive the diagnosis packets (or onlyreceives a subset of the diagnosis packets) from the local opticaltransponder, the local router, in response, does not send echoeddiagnosis packets back to the remote router. The BFD session between thelocal router and the remote router is considered to be down (inoperation) and the remote router is notified of the signal degradationof the optical link in response to not receiving the echoed diagnosispackets from the local router. In response, the remote router caninitiate the failure response mechanisms (e.g., reroute traffic,initiate a Fast Reroute or convergence process) to bypass the degradinglink. In such instances, the remote router can be notified of thedegradation of the optical link sooner than would be the case of solelywaiting on its slower failure detection to identify the failure (e.g., amechanism solely performed at and using information at the remoterouter).

FIG. 5 is a flow chart illustrating a method 500 to perform a routerswitchover process in response to a notification of a degradation,according to an embodiment. The router switchover process 500 can beexecuted at, for example, a processor such as the processor 248 of therouter 201 shown and described with respect to FIG. 2.

At 501, the method includes sending first data packets and diagnosispackets from a local router (e.g., router 201 in FIG. 2) to a firstoptical transponder (e.g., optical transponder 202 in FIG. 2) such thatthe first optical transponder transmits the data packets to a remoterouter (e.g., router 252 in FIG. 2) via a set of optical links and asecond optical transponder. At 502, the method includes receiving, atthe local router, a signal from the remote router in response to thesecond optical transponder (1) identifying, via pre-forward errorcorrection (FEC) bit error rate detection, a degradation of a firstoptical link from the set of optical links, and (2) dropping a subset orthe entirety of the diagnosis packets. At 503, the method includesrerouting second data packets in response to the signal such that theremote router receives the second data packets via a second optical linkfrom the set of optical links. The second optical link is different fromthe first optical link.

Some embodiments described herein relate to a computer storage productwith a non-transitory computer-readable medium (also can be referred toas a non-transitory processor-readable medium) having instructions orcomputer code thereon for performing various computer-implementedoperations. The computer-readable medium (or processor-readable medium)is non-transitory in the sense that it does not include transitorypropagating signals per se (e.g., a propagating electromagnetic wavecarrying information on a transmission medium such as space or a cable).The media and computer code (also can be referred to as code) may bethose designed and constructed for the specific purpose or purposes.Examples of non-transitory computer-readable media include, but are notlimited to: magnetic storage media such as hard disks, floppy disks, andmagnetic tape; optical storage media such as Compact Disc/Digital VideoDiscs (CD/DVDs), Compact Disc-Read Only Memories (CD-ROMs), andholographic devices; magneto-optical storage media such as opticaldisks; carrier wave signal processing modules; and hardware devices thatare specially configured to store and execute program code, such asApplication-Specific Integrated Circuits (ASICs), Programmable LogicDevices (PLDs), Read-Only Memory (ROM) and Random-Access Memory (RAM)devices. Other embodiments described herein relate to a computer programproduct, which can include, for example, the instructions and/orcomputer code discussed herein.

Examples of computer code include, but are not limited to, micro-code ormicroinstructions, machine instructions, such as produced by a compiler,code used to produce a web service, and files containing higher-levelinstructions that are executed by a computer using an interpreter. Forexample, embodiments may be implemented using imperative programminglanguages (e.g., C, Fortran, etc.), functional programming languages(Haskell, Erlang, etc.), logical programming languages (e.g., Prolog),object oriented programming languages (e.g., Java, C++, etc.) or othersuitable programming languages and/or development tools. Additionalexamples of computer code include, but are not limited to, controlsignals, encrypted code, and compressed code.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Where methods described above indicate certain eventsoccurring in certain order, the ordering of certain events may bemodified. Additionally, certain of the events may be performedconcurrently in a parallel process when possible, as well as performedsequentially as described above.

What is claimed is:
 1. An apparatus, comprising: an optical transponderincluding a processor, an electrical interface and an optical interface,the processor operatively coupled to the electrical interface and theoptical interface, the optical interface configured to be operativelycoupled to a plurality of optical links and the electrical interfaceconfigured to be operatively coupled to a router such that the opticaltransponder is configured to be operatively coupled between theplurality of optical links and the router, the processor configured toreceive data packets and diagnosis packets via an optical link from theplurality of optical links, the processor configured to performpre-forward error correction (FEC) bit error rate (BER) detection toidentify a degradation of the optical link from the plurality of opticallinks, the processor configured to drop a subset of the diagnosispackets designated to be transmitted via the optical link in response tothe degradation being identified such that the router is notified of thedegradation of the optical link in response to the subset of thediagnosis packets being dropped.
 2. The apparatus of claim 1, whereinthe diagnosis packets are bidirectional forwarding detection (BFD)packets.
 3. The apparatus of claim 1, wherein the processor isconfigured to drop the entirety of the diagnosis packets such that therouter is notified of the degradation of the optical link in response tothe drop of the entirety of the diagnosis packets being dropped.
 4. Theapparatus of claim 1, wherein a number of the subset of the diagnosispackets is a predetermined number.
 5. The apparatus of claim 1, wherein:the diagnosis packets are first diagnosis packets; the processor isconfigured to change a field of a copy of the first diagnosis packetsindicating the degradation of the optical link to generate seconddiagnosis packets; and the processor is configured to send the seconddiagnosis packets to the router such that the router is notified of thedegradation of the optical link in response to identifying the field ofthe second diagnosis packets being changed.
 6. The apparatus of claim 1,wherein the electrical interface is an Ethernet interface.
 7. Theapparatus of claim 1, wherein the processor is configured to notinterrupt data traffic transmitted via the plurality of optical links.8. The apparatus of claim 1, wherein the processor is configured toidentify the degradation of the optical link in response to a pre-FECBER value meeting a criteria.
 9. The apparatus of claim 1, wherein theprocessor is configured to drop the subset of the diagnosis packetstransmitted via the optical link in response to a pre-FEC BER valuemeeting a criteria and a pre-determined period of time.
 10. Theapparatus of claim 1, wherein: the optical link is a first optical link;the processor is configured to drop the subset of the diagnosis packetsdesignated to be transmitted via the first optical link such that therouter reroutes data traffic to be transmitted via a second optical linkof the plurality of optical links, the second optical link beingdifferent from the first optical link.
 11. The apparatus of claim 1,wherein the optical transponder is configured to be located separatelyfrom the router.
 12. The apparatus of claim 1, wherein the processor isconfigured to not send a control signal to the router in response to thedegradation of the optical link being identified.
 13. The apparatus ofclaim 1, wherein the diagnosis packets are Ethernet Operations,Administration, and Maintenance (E-OAM) packets.
 14. An apparatus,comprising: a memory; and a processor operatively coupled to the memory,the processor configured to be operatively coupled to a first opticaltransponder, the first optical transponder configured to be operativelycoupled to a second optical transponder via a plurality of opticallinks, the second optical transponder configured to be operativelycoupled to a remote router, the processor configured to send first datapackets and diagnosis packets to the first optical transponder such thatthe first optical transponder transmits the data packets to the remoterouter via the plurality of optical links and the second opticaltransponder, the processor configured to receive a signal from theremote router via the first optical transponder and the second opticaltransponder, in response to the second optical transponder (1)identifying, via pre-forward error correction (FEC) bit error ratedetection, a degradation of a first optical link from the plurality ofoptical links, and (2) dropping a subset of the diagnosis packets, theprocessor configured to reroute second data packets in response to thesignal such that the remote router receives the second data packets viaa second optical link from the plurality of optical links.
 15. Theapparatus of claim 14, wherein the diagnosis packets are EthernetOperations, Administration, and Maintenance (E-OAM) packets.
 16. Theapparatus of claim 14, wherein the processor is configured to be locatedseparately from the first optical transponder.
 17. A non-transitoryprocessor-readable medium storing code representing instructions to beexecuted by a processor, the code comprising code to cause the processorto: receive, at an optical transponder, data packets and diagnosispackets via an optical link from a plurality of optical links; performpre-forward error correction (FEC) bit error rate (BER) detection toidentify a degradation of the optical link from the plurality of opticallinks; drop a subset of the diagnosis packets in response to theidentifying of the degradation of the optical link; and send the datapackets without the subset of the diagnosis packets to a router to beoperatively coupled to the optical transponder to notify the router ofthe degradation of the optical link in response to the dropping of thesubset of the diagnosis packets.
 18. The non-transitoryprocessor-readable medium of claim 17, wherein the diagnosis packets arebidirectional forwarding detection (BFD) packets.
 19. The non-transitoryprocessor-readable medium of claim 17, wherein the code comprises codeto cause the processor to identify the degradation of the optical linkin response to a pre-FEC BER value meeting a criteria.
 20. Thenon-transitory processor-readable medium of claim 17, wherein the codecomprises code to cause the processor to drop the subset of thediagnosis packets in response to a pre-FEC BER value meeting a criteriaand a pre-determined period of time.